Earth-boring tools including cutting element profiles configured to reduce work rates

ABSTRACT

Earth-boring tools may include a body including blades projecting therefrom, an axis of rotation, and cutting elements secured to the blades. A profile of the cutting elements intersecting outermost points of cutting faces of the cutting elements as viewed projected rotationally onto a plane may be parabolic from immediately proximate the axis of rotation to a nose point at which a slope of the profile is such that an angle between the profile and a plane perpendicular to the axis of rotation is about 0°. In other embodiments, a first section of the profile may extend at a first slope, and a second section of the profile may extend at a second, different slope. In still other embodiments, a tangent line to the profile may be oriented at an angle of at least 15° at a location proximate to the axis of rotation.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No. 62/538,320, filed Jul. 28, 2017, the disclosure of which is hereby incorporated herein in its entirety by this reference.

TECHNICAL FIELD

This disclosure relates generally to earth-boring tools and methods of making and using earth-boring tools. More specifically, disclosed embodiments relate generally to profile configurations for faces of earth-boring tools that may reduce work rate for cutting elements, reduce bit imbalance, reduce loads borne by cutting elements on at least some selected areas of the bit face, and improve or maintain cutting removal efficiency.

BACKGROUND

Wellbores are formed in subterranean formations for various purposes including, for example, extraction of oil and gas from the subterranean formation and extraction of geothermal heat from the subterranean formation. Wellbores may be formed in a subterranean formation using a drill bit, such as an earth-boring rotary drill bit. Different types of earth-boring rotary drill bits are known in the art, including fixed-cutter bits (which are often referred to in the art as “drag” bits), rolling-cutter bits (which are often referred to in the art as “rock” bits), diamond-impregnated bits, and hybrid bits (which may include, for example, both fixed cutters and rolling cutters). A fixed-cutter drill bit comprises a bit body attached to a shank which will have a threaded portion to connect to the rest of the bottom hole assembly. The bit body will have a crown which contacts the formation to be drilled. In the crown are nozzle inserts for connecting to internal fluid passageways to provide drilling fluid or mud to the face of the bit body. The crown also has junk slots to allow for removal of cuttings from the formation and mud back up to the surface. The crown also has blades, onto which are attached cutting elements which engage and remove the formation material during a drilling operation. The profile of the crown, which may be characterized as the face of the bit is, in a majority of modern drag bits employing polycrystalline diamond compact (PDC) cutters, divided up into regions by their relationship to a longitudinal axis or centerline of the bit. The area near the center of the drill bit, the rotational axis, is referred to as the cone region. From the cone region, moving radially outwardly, other regions of the crown are; the nose, the shoulder, and the gage region. The profile of the crown is such that typically the nose region is the first to contact the formation as the drill bit advances into the formation during drilling.

During drilling, the drill bit is rotated and advanced into the subterranean formation. As the drill bit rotates, the cutters on the face of the bit and extending to the gage, cut and shear the formation material to form the wellbore. A diameter of the wellbore drilled by the drill bit may be defined by the cutting structures disposed at the gage, the largest outer diameter of the drill bit.

The drill bit is coupled, either directly or indirectly, to an end of what is referred to in the art as a “drill string,” which comprises a series of elongated tubular segments connected end-to-end that extends into the wellbore from the surface of earth above the subterranean formations being drilled. Various tools and components, including the drill bit, may be coupled together at the distal end of the drill string at the bottom of the wellbore being drilled. This assembly of tools and components is referred to in the art as a “bottom hole assembly” (BHA).

The drill bit may be rotated within the wellbore by rotating the drill string from the surface of the formation, or the drill bit may be rotated by coupling the drill bit to a downhole motor, which is also coupled to the drill string and disposed proximate the bottom of the wellbore. The downhole motor may include, for example, a hydraulic Moineau-type motor having a shaft, to which the drill bit is mounted, that may be caused to rotate by pumping fluid (e.g., drilling mud or fluid) from the surface of the formation down through the center of the drill string, through the hydraulic motor, out from nozzles in the drill bit, and back up to the surface of the formation through the annular space between the outer surface of the drill string and the exposed surface of the formation within the borehole. The downhole motor may be operated with or without drill string rotation.

Because the drill string can be of considerable length, the drilling assembly and the drill bit can exhibit a variety of motions in addition to the rotation of the drill bit along a linear path. Such motions are generally referred to as dysfunctions and include vibration, displacement of the tool along a direction other than the drilling direction, bending moments and whirl. Whirl occurs in rotating members such as drill strings, drill bits, shafts, etc. Often whirl induces failures in the bottom hole assembly components and damages the drill bit.

The time required to drill a well is greatly affected by the number of times the drill bit must be changed in order to reach the targeted formation. This is the case because each time the bit is changed, the entire string of drill pipe, which may be miles (kilometers) long, must be retrieved from the borehole, section by section. Once the drill string has been retrieved and the new bit installed, the bit must be lowered to the bottom of the borehole on the drill string, which again must be constructed section by section. This process requires considerable time, effort and expense. The length of time that a drill bit may be employed before it must be changed depends upon its rate of penetration (“ROP”), as well as its durability.

BRIEF SUMMARY

In some embodiments, earth-boring tools may include a body including blades projecting therefrom, the blades extending generally radially outwardly from an axis of rotation of the tool. Cutting elements may be secured to the blades. A profile of the cutting elements secured to the blades intersecting outermost points of cutting faces of the cutting elements as viewed projected rotationally onto a plane, within which an axis of rotation of the body may be located, may be parabolic from immediately proximate the axis of rotation to a nose point at which a slope of the profile is such that an angle between the profile and a plane perpendicular to the axis of rotation is about 0°.

In other embodiments, earth-boring tools may include a body having blades extending outward from a remainder of the body. Cutting elements may be secured to the blades. A first section of a profile of a face formed by a least squares fit to outermost points of cutting faces of the cutting elements secured to the blades as viewed projected rotationally onto a plane, within which plane an axis of rotation of the body is located, may be linear and may extend at a first slope relative to a plane perpendicular to the axis of rotation of the body from proximate to the axis of rotation of the body radially outward. A second section of the profile of the face surrounding and extending radially outward from the first section may be linear and may extend at a second, different slope relative to the plane perpendicular to the axis of rotation of the body. A third section of the profile may be located radially outward from the second section, the third section arcing from the second slope away from a leading end of the body.

In still other embodiments, earth-boring tools may include a body having blades extending outward from a remainder of the body. Cutting elements may be secured to the blades. A profile formed by a least squares fit to outermost points of cutting faces of the cutting elements secured may be oriented at an angle of at least 15° relative to a plane perpendicular to an axis of rotation of the body at a location proximate to an axis of rotation of the body.

BRIEF DESCRIPTION OF THE DRAWINGS

While this disclosure concludes with claims particularly pointing out and distinctly claiming specific embodiments, various features and advantages of embodiments within the scope of this disclosure may be more readily ascertained from the following description when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view an earth-boring tool;

FIGS. 2A through 2D are schematics of profiles for cutting elements of an earth-boring tool, such as that shown in FIG. 1;

FIG. 3 is a schematic of two embodiments of profiles for cutting elements for an earth-boring tool, such as that shown in FIG. 1; and

FIG. 4 is a schematic of yet another embodiment of a profile for cutting elements of an earth-boring tool, such as that shown in FIG. 1.

DETAILED DESCRIPTION

The illustrations presented in this disclosure are not meant to be actual views of any particular earth-boring tool or component thereof, but are merely idealized representations employed to describe illustrative embodiments. Thus, the drawings are not necessarily to scale.

As used herein, the term “configured” refers to a size, shape, material composition, and/or arrangement of one or more of at least one structure and at least one apparatus facilitating operation of one or more of the structure and the apparatus in a predetermined way.

As used herein, the terms “substantially” and “about” in reference to a given parameter, property, or condition means and includes to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a degree of variance, such as within acceptable manufacturing tolerances. For example, a parameter that is substantially or about a specified value may be at least about 90% the specified value, at least about 95% the specified value, at least about 99% the specified value, or even at least about 99.9% the specified value.

As used herein, the term “earth-boring tool” means and includes any type of bit or tool used for drilling during the formation or enlargement of a wellbore in a subterranean formation. For example, earth-boring tools include fixed-cutter drill bits, percussion bits, core bits, eccentric bits, bi-center bits, reamers, mills, hybrid bits, and other drilling bits and tools known in the art.

The inventors herein have discovered that, in addition to the form, orientation and positioning of the PDC cutting elements on the bit face, the profile of the bit and particularly the profile portion from the nose through the cone to the bit centerline greatly impact bit durability and ROP. Therefore, the form and positioning of the cutting elements and the design of the bit body are thus are significant to improving ROP and durability of a drill bit.

FIG. 1 shows a perspective view of an earth-boring tool 100. The earth-boring tool 100 may include a body 102 having blades 104 extending outward from a remainder of the body 102 with junk slots 114 located rotationally between the blades 104. The blades 104 may extend radially outward from proximate to the axis of rotation 110 of the earth-boring tool 100 to a gage region 118 at an outer diameter of the body 102. The blades 104 may extend longitudinally from a face 116 of the body 102 at a leading end of the earth-boring tool 100, away from the face 116, toward a shank 120 at a trailing end of the earth-boring tool 100. The shank 120 may have a threaded connection portion, which may conform to industry standards (e.g., those promulgated by the American Petroleum Institute (API)), for attaching the earth-boring tool 100 to a drill string. The body 102 may include a material suitable for downhole use. For example, the body 102 may include a metal or metal alloy material (e.g., steel) or a particle-matrix composite material (e.g., particles of tungsten carbide located in a metal or metal alloy matrix).

Cutting elements 112 may be secured to the body 102. More specifically, the cutting elements 112 may be secured at least partially within pockets 122 extending from rotationally leading surfaces of a blade 104 into the blade 104. The cutting elements 112 may be configured to engage with the formation under WOB, and remove formation material during rotation of the earth-boring tool 100. Nozzles 124 located within the junk slots 114 may emit drilling fluid circulating through the drill string under pressure to remove cuttings from the cutting elements 112 and the bit face and carry the cuttings suspended in the drilling fluid up the wellbore annulus to the surface. The cutting elements 112 of the earth-boring tool 100 may have a profile 106 according to an embodiment of the disclosure, which profile 106 may best be shown by projecting cutting faces 134 of the cutting elements 112 rotationally onto a common plane 108 to one side of an axis of rotation 110, which may also be characterized as the longitudinal axis, of the earth-boring tool 100. The profile 106 may then be formed by identifying the outermost points of the cutting faces 134 of the cutting elements 134, the outermost points being located farthest from the body 102, and calculating a least squares fit for those points. Profiles 106 for cutting elements 112 of earth-boring tools 100 in accordance with this disclosure may reduce the work rate for individual cutting elements 112 secured to face 116 of the earth-boring tool 100, may improve stability of the earth-boring tool 100 during drilling, and may better distribute loads borne across the radial extent of the profile 106 without significantly worsening performance, in terms of rate of penetration (ROP) of the earth-boring tool 100. The earth-boring tool 100 depicted in FIG. 1 is configured as a fixed-cutter drill bit having cutting elements 112 secured to the blades 104 thereof, but other configurations for earth-boring tools employing fixed cutting elements may be employed with a profile 106 for cutting elements 112 in accordance with this disclosure.

FIGS. 2A through 2D are schematic embodiments of profiles 106 for cutting elements 112 of an earth-boring tool, such as the earth-boring tool 100 shown in FIG. 1. The profiles 106A through 106D of FIGS. 2A through 2D may collectively follow a parabolic trajectory 126 from proximate to the axis of rotation 110 of the earth-boring tool 100 (see FIG. 1), radially outward, to a nose point 128. At the nose point 128, a slope of the profiles 106A through 106D as measured relative to a plane 130 extending perpendicular to the axis of rotation 110 may be such that an angle between tangent lines to the profiles 106A through 106 D and the plane 130 at the nose point 128 may be, for example, less than about 5°. More specifically, a line extending tangent to a surface of the blades 104 at the nose point 128 may be, for example, about 0°. From the nose point 128, the profile 106 may extend radially outward to the gage region 118 (see FIG. 1) while curving longitudinally toward the shank 120 (see FIG. 1). The nose point 128 may be located at least one-half of a radius of the earth-boring tool 100 (see FIG. 1) away from the axis of rotation 110. More specifically, the nose point 128 may be located between about one-half and about three-fourths of the radius of the earth-boring tool 100 (see FIG. 1) from the axis of rotation.

The outer surface of each blade 104A through 104D in the region extending radially from the axis of rotation 110 to the nose point 128 may include one or more planes 132A through 132D extending radially outward from the axis of rotation 110 toward the nose point 128, and extending longitudinally at an oblique angle relative to the plane 130 perpendicular to the axis of rotation 110. For example, the outer surface of each blade 104A through 104D may include a number of planes 132A through 132D equal to a number of cutting elements 112A through 112D located in the region extending radially from the axis of rotation 110 to the nose point 128, each cutting element 112A through 112D located on a corresponding one of the planes 132A through 132D. More specifically, the total number of planes 132A through 132D deployed on all the blades 104A through 104D of a given earth-boring tool may be at least five. Each plane 132A through 132D may be oriented tangent to the parabolic trajectory 126 at a point of intersection between the surface of the respective plane 132A through 132D and a line 136A through 136D extending from a point on a cutting face 134A through 134D of a corresponding cutting element 112A, through 112D farthest from the blade 104A through 104D within the plane 132A through 132D, to the respective plane 132A through 132D in a direction perpendicular to the plane 132A through 132D. When the planes 132A through 132D of the blades 104A through 104D are projected rotationally onto the plane 108 (see FIG. 1) containing the axis of rotation 110, the parabolic trajectory 126 may contact each of the planes 132A through 132D, such that the planes 132A through 132D lie tangent to the parabolic trajectory. Moreover, a curve 138 formed by a least squares fit to a series of points generated by rotationally projecting each of the cutting elements 112A through 112D within the region extending radially from the axis of rotation 110 to the nose point 128 onto the plane 108 (see FIG. 1) in which the axis of rotation 110 is located and placing the points at the points on the cutting faces 134A through 134D of the cutting elements 112A through 112D farthest from the surfaces of the blades 104A through 104D within the region may be a parabola.

Because the cutting elements 112A through 112D may be located at different radial distances from the axis of rotation 110, the specific slopes of the planes 132A through 132D relative to the plane 130 perpendicular to the axis of rotation 110 may vary. For example, the slopes of the planes 132A through 132D relative to the plane 130 perpendicular to the axis of rotation 110 may be such that angles between the planes 132A through 132D and the plane 130 perpendicular to the axis of rotation 110 may vary from about 35° or less proximate to the axis of rotation 110 to greater than about 0° proximate to the nose point 128. More specifically, the slopes of the planes 132A through 132D relative to the plane 130 perpendicular to the axis of rotation 110 may be such that angles between the planes 132A through 132D and the plane 130 perpendicular to the axis of rotation 110 may vary from about 30° or less proximate to the axis of rotation 110 to about 5° or more (e.g., about 10° or more, about 15° or more, etc.) proximate to the nose point 128. The parabolic trajectory 126 followed by the planes 132A through 132D of the blades 104A through 104D, and the parabolic curve 138 followed by the cutting elements 112A through 112D, may enable the region proximate to the axis of rotation 110 to extend more rapidly toward the shank 120 (see FIG. 1), while the parabolic trajectory 126 and the parabolic curve 138 may more gradually transition from the steep region proximate to the axis of rotation 110 to the nose point 128.

FIG. 3 is a schematic of embodiments of two additional profiles 106E and 106F for cutting elements 112 (see FIG. 1) for an earth-boring tool, such as the earth-boring tool 100 shown in FIG. 1. As shown in FIG. 3, another profile 106E for cutting elements 112 (see FIG. 1) in accordance with this disclosure may follow a parabolic trajectory 126 in the region extending from the axis of rotation 110 of the earth-boring tool 100 to the nose point 128. As with the previous embodiment, the nose point 128 may be at a location where a slope of the profile 106E may be such that an angle from a line tangent to the profile 106E as measured relative to a plane 130 extending perpendicular to the axis of rotation 110 may be, for example, less than about 5°. More specifically, the nose point 128 may be located where a line extending tangent to a curve 138 defining the profile 106E, and formed by a least squares fit to a series of points generated by rotationally projecting each of the cutting elements 112 (see FIG. 1) onto the plane 108 (see FIG. 1) in which the axis of rotation 110 is located and placing the points on the cutting faces 134A through 134D of the cutting elements 112A through 112D farthest from the surfaces of the blades 104A through 104D within the region, may be, for example, about 0°. From the nose point 128, the profile 106E may extend radially outward to the gage region 118 (see FIG. 1) while curving longitudinally toward the shank 120 (see FIG. 1).

Unlike the outer surfaces of the blades 104A through 104D shown in FIGS. 2A through 2D, which included planes 132A through 132D extending tangent to the parabolic trajectory 126, the outer surface of at least one of the blades 104E shown in FIG. 3 may itself be parabolic. More specifically, the outer surface of the blade 104E when projected rotationally onto the plane 108 (see FIG. 1) in which the axis of rotation 110 is located may be a parabola from immediately proximate to the axis of rotation 110 to the nose point 128, with substantially no linear portions.

A slope of the curve 138 defining the profile 106E relative to the plane 130 perpendicular to the axis of rotation 110, as quantified by measuring an angle between a line tangent to the outer surface and the plane 130 perpendicular to the axis of rotation 110, may vary from about 35° or less proximate to the axis of rotation 110 to about 0° or more proximate to the nose point 128. More specifically, the slope of the curve 138 defining the profile 106E relative to the plane 130 perpendicular to the axis of rotation 110 may be such that the angle between the line tangent to the outer surface and the plane 130 vary from about 30° or less proximate to the axis of rotation 110 to about 5° or more (e.g., about 10° or more, about 15° or more, etc.) proximate to the nose point 128. The slope of the curve 138 defining the profile 106E relative to the plane 130 perpendicular to the axis of rotation 110 may vary continuously from proximate to the axis of rotation 110 to proximate to the nose point 128, forming a parabola. The parabolic trajectory 126 followed by the profile 106E of the blade 104, and the parabolic curve 138 followed by the cutting elements 112 (see FIG. 1) secured thereto, may enable the region proximate to the axis of rotation 110 to extend more rapidly toward the shank 120 (see FIG. 1), while the parabolic trajectory 126 and the parabolic curve 138 may more gradually transition from the steep region proximate to the axis of rotation 110 to the nose point 128.

The other profile 106F shown in FIG. 3 may be characterized by a linear portion 125 of the profile 106F exhibiting a steep slope extending from proximate to the axis of rotation 110, radially outward, to proximate to the nose point 128. From the nose point 128, the profile 106F may extend radially outward to the gage region 118 (see FIG. 1) while curving longitudinally toward the shank 120 (see FIG. 1). A slope of a linear portion 125 of the profile 106F relative to the plane 130 perpendicular to the axis of rotation 110 may be such that an angle between the linear portion 125 and the plane 130 may be, for example, between about 35° and about 10°. More specifically, the slope of the linear portion 125 of the profile 106F relative to the plane 130 perpendicular to the axis of rotation 110 may be such that the angle between the linear portion 125 and the plane 130 may be between about 30° and about 15°. The steep slope of the linear portion 125 of the profile 106F in the region extending from proximate to the axis of rotation 110, radially outward, to proximate to the nose point 128 may enable the region proximate to the longitudinal axis of rotation 110 to extend more rapidly toward the shank 120 (see FIG. 1). The profile 106F may be generated by, for example, forming a least squares fit to a series of points identified by rotationally projecting each of the cutting elements 112 (see FIG. 1) onto the plane 108 (see FIG. 1) in which the axis of rotation 110 is located and placing the points on the cutting faces 134 (see FIG. 1) of the cutting elements 112 (see FIG. 1) farthest from the surfaces of the blades 104 (see FIG. 1).

In some embodiments employing the steep linear trajectory for the profile 106F of the cutting elements 112 proximate to the axis of rotation 110, the nose point 128 may be located on a planar nose surface 127. For example, the surfaces of the blades 104 (see FIG. 1) producing the linear portion 125 of the profile 106F, which may themselves be planar, may intersect with another planar nose surface 127 at an edge. The nose surface 127 may extend radially outward from the surfaces of the blades 104 (see FIG. 1) producing the steep linear portion 125 of the profile 106F at a slope such that an angle between the nose surface 127 and the plane 130 extending perpendicular to the axis of rotation 110 may be less than about 5°. More specifically, the slope of the nose surface 127 may be such that the angle between the nose surface 127 and the plane 130 extending perpendicular to the axis of rotation 110 may be, for example, about 0°. From the nose surface 127, the surfaces of the blades 104 may extend radially outward to the gage region 118 (see FIG. 1) while curving longitudinally toward the shank 120 (see FIG. 1).

FIG. 4 is a schematic of yet another embodiment of a profile 106G of cutting elements 112 (see FIG. 1) for an earth-boring tool, such as the earth-boring tool 100 shown in FIG. 1. The profile 106G shown in FIG. 3 may be characterized by a first linear section 140 exhibiting a steeper slope extending from proximate to the axis of rotation 110 radially outward to a second linear section 142, the second linear section 142 extending from the first linear section 140 at a shallower slope to or proximate to the nose point 128. As with the previous embodiment, the nose point 128 may be at a location where a slope of the profile 106G may be at or proximate a minimum, as quantified by measuring an angle between a line tanged to the profile 106G at the nose point and a plane 130 extending perpendicular to the axis of rotation 110, which may be, for example, less than about 5°. More specifically, the nose point 128 may be located where a line extending tangent to the profile 106G may be, for example, about 0°. From the nose point 128, the profile 106G may extend radially outward to the gage region 118 (see FIG. 1) while curving longitudinally toward the shank 120 (see FIG. 1). The profile 106G may be generated by, for example, forming a least squares fit to a series of points corresponding to locations on the cutting faces 134 (see FIG. 1) of the cutting elements 112 (see FIG. 1) farthest from the surfaces of the blades 104 (see FIG. 1) when the cutting faces 134 (see FIG. 1) are rotationally projected onto the plane 108 (see FIG. 1) in which the axis of rotation 110 is located.

A slope of the first linear section 140 of the profile 106G relative to the plane 130 perpendicular to the axis of rotation 110 may be such that an angle between the first linear section 140 and the plane 130 may be, for example, between about 35° and about 5°. More specifically, the slope of the first linear section 140 of the profile 106G relative to the plane 130 perpendicular to the axis of rotation 110 may be such that an angle between the first linear section 140 and the plane 130 may be, for example, between about 30° and about 10°. A first radial distance R₁ over which the first linear section 140 extends, as measured from the axis of rotation 110 in a direction perpendicular to the axis of rotation 110, may be, for example, between about 50% and about 75% of a second radial distance R₂ to the nose point 128. More specifically, the first radial distance R₁ over which the first linear section 140 extends may be, for example, between about 60% and about 70% (e.g., about 66%) of the second radial distance R₂ to the nose point 128. A slope of the second linear section 142 of the profile 106G relative to the plane 130 perpendicular to the axis of rotation 110 may be less than the slope of the first linear section 140. For example, the slope of the second linear section 142 relative to the plane 130 perpendicular to the axis of rotation 110 may be between about 25% and about 50% of the slope of the first linear section 140. More specifically, the slope of the second linear section 142 relative to the plane 130 perpendicular to the axis of rotation 110 may be between about 30% and about 40% (e.g., about 33%) of the slope of the first linear section 140. As an additional example, the slope of the second linear section 142 relative to the plane 130 perpendicular to the axis of rotation 110 may be such that an angle between the second linear section 142 and the plane 130 may be between about 10° and about 20°. More specifically, the slope of the second linear section 142 relative to the plane 130 perpendicular to the axis of rotation 110 may be such that an angle between the second linear section 142 and the plane 130 may be between about 12° and about 18° (e.g., about 15°). The first slope of the first linear section 140 may be, for example, about one-and-a-half to five times as great as the second slope of the second linear section 142 relative to the plane perpendicular to the axis of rotation of the body. More specifically, the first slope of the first linear section 140 may be, for example, about two to four times (e.g., two-and-a-half times, three times, three-and-a-half times) as great as the second slope of the second linear section 142 relative to the plane perpendicular to the axis of rotation of the body. The steeper slope of the first linear section 140 may enable the region proximate to the axis of rotation 110 to extend more rapidly toward the shank 120 (see FIG. 1), while the more gradual slope of the second linear section 142 may more gradually transition from the steep region proximate to the axis of rotation 110 to the nose point 128.

Profiles for outermost points of cutting elements of earth-boring tools in accordance with this disclosure may exhibit a deeper cone region immediately surrounding the axis of rotation. As a result a greater quantity of the formation material being drilled may be received into the cone region, and the sloped surfaces of the blades may better grip that larger quantity of formation material, increasing stability. In addition, the inventors have found that providing a more gradual transition from the steeper slope in the region proximate to the axis of rotation to a shallower slope proximate to the nose point more evenly balances work rates across the face of the tool. Impact loading of cutting elements following profiles in accordance with this disclosure may also be reduced. The inventors have also found through their modeling of the behavior of an earth-boring tool including profiles for cutting elements in accordance with this disclosure that maximum stresses within the blades are more evenly balanced from blade to blade. Because the slope of the transition between cutting elements secured to the blades is steeper in the cone region, the junk slots within that region may be shallower than in other regions. However, modeling of the fluid flow from the nozzles to clear cuttings reveals that the shallower junk slots do not have a significant deleterious effect on the efficiency with which the fluid clears the cuttings. Finally, earth-boring tools employing profiles in accordance with this disclosure may more evenly distribute a given applied weight (e.g., weight-on-bit) across all the cutting elements.

Additional, nonlimiting embodiments within the scope of this disclosure include the following:

Embodiment 1

An earth-boring tool comprising: a body comprising blades projecting therefrom, the blades extending generally radially outwardly from an axis of rotation of the tool; and cutting elements secured to the blades; wherein a profile of the cutting elements secured to the blades intersecting outermost points of cutting faces of the cutting elements as viewed projected rotationally onto a plane, within which an axis of rotation of the body is located, is parabolic from immediately proximate the axis of rotation to a nose point at which a slope of the line is such that an angle between the line and a plane perpendicular to the axis of rotation is about 0°.

Embodiment 2

The earth-boring tool of Embodiment 1, wherein a slope of the profile proximate to the axis of rotation of the body is such that an angle between the line and a plane perpendicular to the axis of rotation is at least about 15°.

Embodiment 3

The earth-boring tool of Embodiment 1 or Embodiment 2, wherein a slope of the profile proximate to the axis of rotation of the body is such that an angle between the line and a plane perpendicular to the axis of rotation is about 35° or less.

Embodiment 4

The earth-boring tool of any one of Embodiments 1 through 3, wherein the nose point is located at least one-half of a radius of the body from the axis of rotation.

Embodiment 5

The earth-boring tool of any one of Embodiments 1 through 4, wherein the nose point is located at less than three-fourths of a radius of the body from the axis of rotation.

Embodiment 6

The earth-boring tool of any one of Embodiments 1 through 5, wherein surfaces of the blades as projected onto the plane perpendicular to the direction of rotation of the blades comprise a plurality of line segments, each line segment extending tangent to a parabolic curve extending from proximate to the axis of rotation to proximate to the nose point.

Embodiment 7

The earth-boring tool of Embodiment 6, wherein a number of the line segments is at least five.

Embodiment 8

An earth-boring tool comprising: a body comprising blades extending outward from a remainder of the body; and cutting elements secured to the blades; wherein a first section of a profile of a face formed by a least squares fit to outermost points of cutting faces of the cutting elements secured to the blades as viewed projected rotationally onto a plane, within which plane an axis of rotation of the body is located, may be linear and may extend at a first slope relative to a plane perpendicular to the axis of rotation of the body from proximate to the axis of rotation of the body radially outward; wherein a second section of the profile of the face surrounding and extending radially outward from the first section may be linear and may extend at a second, different slope relative to the plane perpendicular to the axis of rotation of the body; and wherein a third section of the profile may be located radially outward from the second section, the third section arcing from the second slope away from a leading end of the body.

Embodiment 9

The earth-boring tool of Embodiment 8, wherein the first slope is two to four times as great as the second slope relative to the plane perpendicular to the axis of rotation of the body.

Embodiment 10

The earth-boring tool of Embodiment 8 or Embodiment 9, wherein the first slope is such that an angle between the first section and a plane perpendicular to the axis of rotation is between about 10° and about 35° relative to the plane perpendicular to an axis of rotation of the body.

Embodiment 11

The earth-boring tool of any one of Embodiments 8 through 10, wherein the second slope is such that an angle between the second section and a plane perpendicular to the axis of rotation is between about 10° and about 20° relative to the plane perpendicular to the axis of rotation of the body.

Embodiment 12

The earth-boring tool of any one of Embodiments 8 through 11, wherein a transition between the first slope and the second slope occurs a radial distance at least about one-half of a radial distance occupied by the first and second slopes.

Embodiment 13

The earth-boring tool of any one of Embodiments 8 through 12, wherein a transition between the first slope and the second slope occurs a radial distance less than about three-fourths of a radial distance occupied by the first and second slopes.

Embodiment 14

An earth-boring tool comprising: a body comprising blades extending outward from a remainder of the body; and cutting elements secured to the blades; wherein a profile formed by a least squares fit to outermost points of cutting faces of the cutting elements secured is oriented at an angle of at least 15° relative to a plane perpendicular to an axis of rotation of the body at a location proximate to an axis of rotation of the body.

Embodiment 15

The earth-boring tool of Embodiment 14, the profile is oriented at an angle of about 30° or less relative to the plane perpendicular to the axis of rotation at the location proximate to the axis of rotation.

Embodiment 16

The earth-boring tool of Embodiment 14 or Embodiment 15, wherein the profile is parabolic from immediately proximate the axis of rotation to a nose point at which a slope of the profile is such that an angle between a line tangent to the profile and a plane perpendicular to the axis of rotation is about 0°.

Embodiment 17

The earth-boring tool of Embodiment 16, wherein the nose point is located at least one-half of a radius of the body from the axis of rotation.

Embodiment 18

The earth-boring tool of Embodiment 16, wherein the nose point is located at less than three-fourths of a radius of the body from the axis of rotation.

Embodiment 19

The earth-boring tool of Embodiment 14, wherein surfaces of the blades as projected onto a plane perpendicular to a direction of rotation of the blades comprise a plurality of line segments, each line segment extending tangent to a parabolic curve extending from proximate to the axis of rotation to proximate to the nose point.

Embodiment 20

The earth-boring tool of Embodiment 19, wherein a number of the line segments is at least five.

While certain illustrative embodiments have been described in connection with the figures, those of ordinary skill in the art will recognize and appreciate that the scope of this disclosure is not limited to those embodiments explicitly shown and described in this disclosure. Rather, many additions, deletions, and modifications to the embodiments described in this disclosure may be made to produce embodiments within the scope of this disclosure, such as those specifically claimed, including legal equivalents. In addition, features from one disclosed embodiment may be combined with features of another disclosed embodiment while still being within the scope of this disclosure, as contemplated by the inventors. 

What is claimed is:
 1. An earth-boring tool comprising: a body comprising blades projecting therefrom, the blades extending generally radially outwardly from an axis of rotation of the tool; and cutting elements secured to the blades; wherein a profile of the cutting elements secured to the blades intersecting outermost points of cutting faces of the cutting elements as viewed projected rotationally onto a plane, within which an axis of rotation of the body is located, is parabolic from immediately proximate the axis of rotation to a nose point at which a slope of the profile is such that an angle between the profile and a plane perpendicular to the axis of rotation is about 0°.
 2. The earth-boring tool of claim 1, wherein a slope of the profile proximate to the axis of rotation of the body is such that an angle between the profile and a plane perpendicular to the axis of rotation is at least about 15°.
 3. The earth-boring tool of claim 1, wherein a slope of the profile proximate to the axis of rotation of the body is such that an angle between the profile and a plane perpendicular to the axis of rotation is about 35° or less.
 4. The earth-boring tool of claim 1, wherein the nose point is located at least one-half of a radius of the body from the axis of rotation.
 5. The earth-boring tool of claim 1, wherein the nose point is located at less than three-fourths of a radius of the body from the axis of rotation.
 6. The earth-boring tool of claim 1, wherein surfaces of the blades as projected onto the plane perpendicular to the direction of rotation of the blades comprise a plurality of line segments, each line segment extending tangent to a parabolic curve extending from proximate to the axis of rotation to proximate to the nose point.
 7. The earth-boring tool of claim 6, wherein a number of the line segments is at least five.
 8. An earth-boring tool comprising: a body comprising blades extending outward from a remainder of the body; and cutting elements secured to the blades; wherein a first section of a profile of a face formed by a least squares fit to outermost points of cutting faces of the cutting elements secured to the blades as viewed projected rotationally onto a plane, within which plane an axis of rotation of the body is located, may be linear and may extend at a first slope relative to a plane perpendicular to the axis of rotation of the body from proximate to the axis of rotation of the body radially outward; wherein a second section of the profile of the face surrounding and extending radially outward from the first section may be linear and may extend at a second, different slope relative to the plane perpendicular to the axis of rotation of the body; and wherein a third section of the profile may be located radially outward from the second section, the third section arcing from the second slope away from a leading end of the body.
 9. The earth-boring tool of claim 8, wherein the first slope is two to four times as great as the second slope relative to the plane perpendicular to the axis of rotation of the body.
 10. The earth-boring tool of claim 8, wherein the first slope is such that an angle between the first section and a plane perpendicular to the axis of rotation is between about 10° and about 35° relative to the plane perpendicular to an axis of rotation of the body.
 11. The earth-boring tool of claim 8, wherein the second slope is such that an angle between the second section and a plane perpendicular to the axis of rotation is between about 10° and about 20° relative to the plane perpendicular to the axis of rotation of the body.
 12. The earth-boring tool of claim 8, wherein a transition between the first slope and the second slope occurs a radial distance at least about one-half of a radial distance occupied by the first and second slopes.
 13. The earth-boring tool of claim 8, wherein a transition between the first slope and the second slope occurs a radial distance less than about three-fourths of a radial distance occupied by the first and second slopes.
 14. An earth-boring tool comprising: a body comprising blades extending outward from a remainder of the body; and cutting elements secured to the blades; wherein a profile formed by a least squares fit to outermost points of cutting faces of the cutting elements secured is oriented at an angle of at least 15° relative to a plane perpendicular to an axis of rotation of the body at a location proximate to an axis of rotation of the body.
 15. The earth-boring tool of claim 14, the profile is oriented at an angle of about 30° or less relative to the plane perpendicular to the axis of rotation at the location proximate to the axis of rotation.
 16. The earth-boring tool of claim 14, wherein the profile is parabolic from immediately proximate the axis of rotation to a nose point at which a slope of the profile is such that an angle between a line tangent to the profile and a plane perpendicular to the axis of rotation is about 0°.
 17. The earth-boring tool of claim 16, wherein the nose point is located at least one-half of a radius of the body from the axis of rotation.
 18. The earth-boring tool of claim 16, wherein the nose point is located at less than three-fourths of a radius of the body from the axis of rotation.
 19. The earth-boring tool of claim 14, wherein surfaces of the blades as projected onto a plane perpendicular to a direction of rotation of the blades comprise a plurality of line segments, each line segment extending tangent to a parabolic curve extending from proximate to the axis of rotation to proximate to the nose point.
 20. The earth-boring tool of claim 19, wherein a number of the line segments is at least five. 